Efficient and timely charging of mobile electronic devices are important to users, and can differentiate the popularity of one device over another. To estimate energy storage device (e.g., battery) voltage, existing charging methods rely on a Kelvin connection to compensate for circuit board drops and an approximated value of internal energy storage device resistance to estimate the internal voltage drop of the energy storage device. However, because the actual internal energy storage device resistance value is not known, and moreover, varies with temperature, state of charge, etc., existing charging methods leave safe margins within their estimates to prevent energy storage device damage. Accordingly, existing methods do not provide for the most accurate or expedient charging of energy storage devices.
FIG. 1 illustrates generally an example prior art charging circuit, including a charge regulator 105 and a battery 110. The charge regulator 105 is configured to receive a reference voltage and a terminal voltage of the battery 110, and to provide a charging current to the battery 110 using the reference voltage and the terminal voltage.